Lubricant compositions



3,222,279 LUBRICANT COMPOSITIONS Donald E. Loefiler, Walnut Creek, Calif., assiguor to Shell Oil Company, New York, N.Y., a corporation of Delaware No Drawing. Filed June 25, 1963, Ser. No. 290,345 12 Claims. (Cl. 252--28) This invention relates to lubricating grease compositions useful at very high temperatures. More particularly, it relates to clay-thickened greases which are capable of use in high-temperature applications, and which are, at the same time, resistant to disintegration in the presence of water.

The manufacture of greases gelled with inorganic colloids and particularly with clay has been disclosed in the prior art. In order to maintain the water stability of such greases, it is necessary to provide the clay with hydrophobic surfaces or otherwise to protect it. Various means for achieving this have been proposed in the art such as providing hydrophobic surface-active agents including amines, imidazolines, amidoamines and the like. Even though the structure of such greases is stable at extremely high temperatures, most conventional surfactant-containing clay-thickened greases are inadequate for use at high temperatures because of the thermal and/or oxidation instability of the surfactant itself. This special high-temperature problem has been solved to some extent by the water-proofing of such greases with thermally stable thermosetting resins, instead of relatively unstable cationic surfactants. However, lubricating compositions suitable for general use throughout the mechanical arts should possess good lubricating properties when operated in either a dry or wet environment. This latter condition is particularly prevalent in such industrial uses as steel rolling mill applications and the like. Furthermore, the yield of greases prepared from such gelling agents must be as high as possible. The use of resin-coated gelling agents per se has by no means been a panacea for these latter two problems.

It is, therefore, an object of this invention to provide new clay-thickened grease compositions suitable for use at extremely high temperatures, which are resistant to the leaching action of water and which can be produced with only a small amount of clay gelling agent.

Now, in accordance with the present invention, it has been found that greases exhibiting high water resistance and excellent thermal stability at extremely high temperature, both at high yield comprise a lubricating oil gelled to a grease consistency with a colloidally dispersed clay, bearing on its surfaces a resin formed from the reaction of a polyepoxide with an amine curing agent, the resinto-clay weight ratio being at least about 0.7. Preferably the compositions comprise an organosilicone fluid of lubricating oil viscosity gelled to a grease consistency with a colloidally dispersed clay, the surfaces of the clay hearing the above-mentioned proportions of amine-cured epoxide resin.

The colloidal gelling or thickening agents to be employed are especially selected for use in high-temperature grease compositions due to their relatively inert character at these high operating temperatures. While clays of low base exchange capacity, such as Georgia clay, Attapulgite and the like, may be utilized, it is preferred that a high base exchange clay, such as Wyoming bentonite or Hectorite, be employed.

While the present invention is especially directed to extreme high-temperature lubricating greases, such greases may be employed for normal operating conditions as well. Likewise, superior greases for less severe applications can also be made in accordance with the invention by selec- "Unitcd States Patent as Ce tion of the lubricating oil base stock. In this regard, most mineral oils are stable up to about 300 F., synthetic esters are useful at temperatures up to about 350-400 F. In this latter category are synthetic lubricating oils of known types, such as the phosphorus esters, silicon esters and aliphatic esters formed by esterification of aliphatic dicarboxylic acids with monohydric alcohols, and polyphenyl ethers. Typical species of these materials include tricresyl phosphate, dioctyl phthalate, bis(Z-ethylhexyl) secabate, and the like.

Lubricants to be employed at temperatures in excess of about 400 F. are those having an inherent high thermal stability including the halocarbons and organo-silicone fluids. The halocarbons may be those described in Peterson et a1 patent, US. 2,679,479, and include especially the fluorocarbon oils, preferably distilling above about 200 C. at atmospheric pressure. The most useful class of lubricants for grease compositions to be utilized at temperatures in excess of about 400 F. include the organo substituted silicone fluids of lubricating oil viscosity. Of primary interest for this invention are the unreactive, thermally stable silicone fluids, which will generally be of the following types.

Methyl silicone fluids:

The above types of silicone fluids, in addition to being the most thermally stable, are also the most readily available in commercial quantities. Methyl phenyl fluids are particularly preferred because of their still greater thermal stability.

It will, of course, be recognized, that other organic groups as well as inorganic groups can replace a portion of the methyl groups, e.g., hydrogen, lower alkyls, halogens, etc. They are, however, generally too reactive and/ or thermally instable for high-temperature applications, though from the standpoint of mere grease formation and use at temperatures at which they are stable, they are quite satisfactory for the grease compositions of the invention.

The polyepoxides used in the process of the invention comprise those organic materials possessing more than one Vic-epoxy group, i.e., more than one o C C group and having no groups highly reactive to water. These materials'may be saturated or unsaturated, aliphatic, cycloaliphatic, aromatic or heterocyclic. They should not, howevempossess groups, such as isocyanate groups, which are highly reactive toward water.

For clarity, many of the polyepoxides and particularly those of the polymeric type will be described in terms of epoxy equivalent value. The meaning of this expression is described in US. 2,633,458.

- If the polyepoxide consists of a single compound and all of the epoxy groups are intact, the epoxy equivalency will be integers, such as 2, 3, 4 and the like. However,

in the case of polymeric type polyepoxides, many of the materials may contain some of the monomeric monoepoxides or have some of their epoxy groups hydrated or otherwise reacted and/or contain macromolecules of somewhat different molecular weight so that epoxy equivalent values may be quite low and contain fractional values. The polymeric material may, for example, have epoxy equivalent values, such as 1.5, 1.8, 2.5 and the like.

Examples of the polyepoxides include, among others, l,4-bis(2,3-epoxypropoxy)benzene, l,3-bis(2,3-epoxypropoxy)benzene, 4,4-bis(2,3-propoxy)diphenyl e-ther, 1,8- bis(2,3-epoxypropoxy)octane, 1,4-bis(2,3-epoxypropoxy) cyclohexane, 4,4'-bis(2-methoxy-3,4-epoxybutoxy)-diphenyl dimethylmethane, 1,3-bis(4,5-epoxypentoxy)-5- chlorobenzene, 1,4-bis 3 ,4-epoxybutoxy -2-chlorocyclohexane, 1,3-bis(2-methoxy-3,4-epoxybutoxy)benzene, and 1,4-bis(2-methoxy-4,5-epoxypentoxy)benzene.

Other examples include the epoxy polyethers of polyhydric phenols obtained by reacting a polyhydric phenol with a halogen-containing epoxide or dihalohydrin in the presence of an alkaline medium. Polyhydric phenols that can be used for this purpose include, among others, resorcinol, catechol, hydroquinone, methyl resorcinol, or polynuclear phenols, such as 2,2-bis(4-hydroxyphenyl) propane (Bisphen-ol A), 2,2 bis(4 hydroxyphenyl) butane, 4,4 dihydroxybenzophenone, bis (4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)pentane and 1,5- dihydroxynaphthalene. The halogen-containing epoxides may be further exemplified by 3-chloro-l,2epoxybutane, 3-bromo-1,2-epoxyhexane, 3-chloro-1,2-epoxyoctane; and the like.

The monomer products produced by this method from dihydric phenols and epichlorohyd-rin may be represented by the general formula wherein R represents a divalent hydrocarbon radical of the dihydric phenol. The polymeric products will generally not be a single simple molecule but will be a complex mixture of glycidyl polyethers of the general formula wherein R is a divalent hydrocarbon radical of the dihydric phenol and n is an integer of the series 0, 1, 2, 3, etc. While for any single molecule of the polyether n is an integer, the fact that the obtained polyether is a mixture of compounds causes the determined value for n t-o be an average which is not necessarily zero or a whole number.

The amine curing agents to be used with the abovedescribed polyepoxides in the process of the invention to convert the polyepoxide to an insoluble, infusible form are preferably organic materials possessing a plurality of amino hydrogen, i.e., a plurality of groups wherein N is an amino nitrogen. These include the aliphatic, cycloaliphatic, aromatic or heterocyclic polyamines as well as derivatives thereof as long as the derivative still contains the necessary amino hydrogen.

Examples of these materials include, among others, the aliphatic polyamines, such as, for example, ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, 1,4- aminobutane, 1,3-diaminobutane, hexamethylene diamine, 3 (n-isopropylamino)propylamine, N,N'-diethyl-l,3-propanediamine, hexapropylene heptamine, penta(l-methylpropylene)hexamine, tetrabutylenepentamine, hexa(l,1 dimethylethylene)heptamine, di(1 methylbutylene)triamine, pentaamylhexamine, tri(1,2,2-trimethylethylene)tetramine, tetra(l,3-dimethylpropylene)pentamine, penta(1,5-dimethylamylene) hexamine, penta(1,2-dimethyl-1-isopropylethylene)hex amine and N,N'-dibutyl.-1,6-hexanediamine.

Aliphatic polyamines coming under special consideration are the alkylene polyamines of the formula wherein R is an alkylene radical, or a hydrocarbon-substituted alkylene radical, and n is an integer of at least one, there being no upper limit to the number of alkylene groups in the molecule.

Especially preferred aliphatic polyamines comprise the polyethylene polyamines of the formula HzN{CH2CH2 1 n wherein n is an integer varying from about 2 to 8. Coming under special consideration are the polyethylene polyamines comprising 20-80% by weight of polyethylene polyamines having average molecular weights in the range of 200500. These high molecular weight polyethylene polyamines normally start with tetraethylene pentamine and having related higher polymers which increase in complexity with increasing molecular weights. The remaining -20% of the mixture is diethylene triamine employed in such proportions that the mixture is fiuid at about room temperature (60-90" F.).

The mixture of high molecular weight polyethylene polyamines is normally obtained as a bottom product in the process for the preparation of ethylene diamine. Consequently, it normally constitutes a highly complex mixture and even may include small amounts (less than about 3% by Weight) of oxygenated materials. A typical mixture o-f polyethylene polyamines diluted with about 25% diethylene triamine has the following analysis:

Percent by weight total basicity, equivalents per grams=l.98, equivalent to 27.7% nitrogen.

Active nitrogen percent 81 Viscosity poises 75-250 Equivalent weight percent 42.5 to 47.5

This mixture of polyamines will be referred to hereinafter as Polyamine H.

7 Other examples include the polyamines possessing cycloaliphatic ring or rings, such as, for example, l-cyclohexylamino-B-aminopropane, 1,4-diaminocyclohexane, 1,3-diaminocyclopentane, di(aminocyclohexyl) -methane, di (aminocyclohexyl)sulfone, l,3-di(aminocyclohexyl)propane, 4-isopropyl-1,Z-diaminocyclohexane, 2,4-diaminocyclohexane, N,N-diethyl-1,4-diaminocyclohexane, and the like. Preferred members of this group comprise those polyamines having at least one amino or alkyl-substituted amino group attached directly to a cycloaliphatic ring containing from 5 to 7 carbon atoms. These cycloaliphatic amines are preferably obtained by hydrogenating the corresponding aromatics amine. Thus di(aminocyc'lohexyl)methane is obtained by hydrogenating methylene dianiline.

Another group of materials that may be used in the process of the invention comprise the organo-metallic compounds, such as those having a silicon or boron atom or atoms linked to amino or substituted amino groups. The compounds may also be those organo-metallic compounds wherein the amino group or substituted amino group or groups are attached to carbon, such as in the alkoxysilylpropylamines as triethoxysilylpropylamines.

Still another group comprises the aminoalkyl-substituted aromatic compounds, such as, for example, di(aminoethyl) benzene, di(aminomethyl)benzene, tri(aminoethyl) benzene, tri(aminobutyl)naphthalene and the like.

Still another group comprises the polymeric polyamines, such as may be obtained by polymerizing or copolymerizing unsaturated amines, such as allyl amine or diallyl amine, alone or with other ethylenically unsaturated compounds. Alternatively, such polymeric products may also be obtained :by forming polymers or copolymers having groups reactive with amines, such as, for example, aldehyde groups, as present on acrolein and methacrolein polymers, and reacting these materials with monomeric amines to form the new polymeric polyamine-s. Still other polymeric amines can be formed by preparing polymers containing ester groups, such as, for example, a copolymer of octadecene-l and methyl acrylate, and then reacting this with a polyamine so as to effect an exchange of an ester group for an amide group and leave the other amine group or groups free. Polymers of this type are described in US. 2,912,416. 1

Still other materials include the N-(aminoalkyl) piperazines, such as, for example, N-aminobutylpiperazine, N-aminoisopropyl-3-butoxypiperazine, N-aminoethylpiperazine, 2,5-dibutyl-N-aminoethyl-piperazine, 2,5- dioctyl-N-aminoisobutylpiperazine and the like. Coming under special consideration are the N-(aminoa-lkyl) piperazines where the alkyl group in the aminoalkyl portion of the molecule contains no more than 6 carbon atoms, and the total molecule contains no more than 18 carbon atoms.

Various monoamines may also be used, among which are secondary amines such as dimethylamine, diethy-lamine, dipropylamine dibutylamine, d'i(tert-butyl)amine, dinonylamine, dicyclohexylamine, diallylarnine, dibenzylamine, methylethylamine, ethylcyclohexylamine and the like.

Because. of the wide variety and diverse chemical characteristics of the available amine curing agents, the relative proportions of the epoxide and the amine curing agent required to obtain effective curing vary widely within a controlled range. In the case of curing agents having an active hydrogen atom (e.g., amines and amides), a curing amount of epoxide curing agent ranges from as little as 0.5 to as high as five times the stoichiometric amount required to react completely with the epoxide. From about 0.8 to about four times the stoichiometric value is preferred, however; and from about one to two times the stoichiometric value isstill further preferred for effective curing.

In the case of curing agents having a catalytic effect on curing rate (e.g., tertiary amines) the relative amountof curing agent is not expressed relative to stoichiometric value, but on a relative Weight basis. Thus, in the case of catalytic curing agents, an amount of curing agent equivalent to 0.1 to 30% by weight of the polyepoxide has been found to be effective. Amounts from about 5% to about by weight are preferred, however. Amine curing agents having active hydrogen groups are those which have at least one replaceable hydrogen atom on one or more nitrogen atoms contained in the molecule.

In order for the resultant grease composition to have satisfactory lubricating properties upon prolonged exposure to evaporation and oxidation, it is imperative that the weight ratio of the resin to the clay be confined to certain limits. Specifically, it has been found that if the resin-to-clay ratio is less than 0.7, the grease may become too fluid upon prolonged exposure to high-temperature operating conditions. A resin-to-clay weight ratio of between 1.0 and 1.5 is especially preferred. Though larger amounts of resin, up to five times the clay weight, may be used, the effectiveness of such heavily coated clay to form a stable grease structure is reduced thereby.

Little has been said herein about the process for preparing the greases of the invention since many such procedures are well known in the art. The grease compositions of the invention may, however, be prepared by either direct or indirect transfer of the resin-coated clay from an aqueous phase to an oil phase. Whatever procedures may be used, all have in common the preparation of an aqueous slurry of the clay prior to forming the resin thereon. It is, however, a necessary limitation to the a compositions of the invention that they be prepared from an aqueous clay dispersion which has been acidified with a strong mineral acid.

Depending upon the physical properties of the particular clay used, the aqueous dispersion or suspension may be a fairly non-viscous slurry or it may be in the form of a hydrogel. Though the form of the dispersion is not an essential aspect of the invention, the preferred clays do form a hydrogel upon dispersion in Water. Normally, in order to keep the clay hydrogel in workable (fiuid) concentration, it is preferred that the clay be dispersed to yield a hydrogel containing between about 0.25% and about 3% by Weight of dry clay, based on the hydrogel before mechanical separation of water therefrom. This percentage is based upon dry weight of de-gangued clay and not upon the dry weight of clay containing naturally occurring contaminants. While the clay is largely dispersed throughout the entire body of the Water in which it is incorporated, it is in the form of jelly-like colloidal globules which can be isolated by mechanical separation from a large part of the water to yield a clay hydrogel of substantially increased clay content Without shrinking the expanded colloidal structure of the clay. By mechanical separation is meant any process for the separation of water from the colloid which does not involve a change in physical state such as occurs in normal evaporation methods and the like. Consequently, mechanical separation normally includes filtration techniques and accelerated substitutes therefor, such as centrifuging. This mechanical separation is performed subsequent to the addition to the clay hydrogel of the above-described resinforming compounds. The mechanical separation can take place at any desired temperature, room temperature being that preferably employed, although any temperature up to that of the boiling point of water may be utilized.

It is an essential step in the process to add a minor amount of a strong mineral acid to the clay dispersion prior to incorporation of the resin-forming compounds. More particularly, the acid must be added in an amount at least sufficient to acidify the surfaces of the clay particles. The quantitative amount of acid to acidify the clay, i.e., to replace all the basic metals (mostly sodium, potassium and calcium) contained on the clay will vary, depending upon the acid which is used and the base exchange capacity of the clay. However, in the case of Hectorite clay to be acidified with phosphoric acid, the amount of acid must be at least 7% by weight of the dry clay. Larger amounts of acid can be used, but no further advantage is obtained thereby, and the excess must be removed before milling of the grease. Though phosphoric acid is the preferred strong mineral acid, other mineral acids such as hydrochloric and sulfuric acid may be employed.

The preferred process for making the grease compositions of the invention is as follows: (1) forming an aqueous colloidal suspension (hydrosol) of degangued clay (usually a hydrogel); (2) admixing with the hydrogel a mineral acid to acidify the clay surfaces and the resinforming coreactants; (3) heating the admixture of hydrogel, resin-forming coreactants to at least the boiling point of water and maintaining the admixture at such tempera ture for a period of at least ten minutes; (4) filtering the reaction mixture to remove at least about 50% of the water therefrom; (5) mixing with the filtered residue (pearls) the lubricating base oil; (6) substantially dehydrating the mixture of residue and base oil by heating to a temperature of at least 250 F.; and (7) milling the dehydrated admixture to form a grease.

An alternative to the above process is to add at least about half of the lubricating base oil to the admixture of hydrosol and resin-forming compounds prior to heating the admixture to effect curing of the polyepoxide resin. In some instances, this procedure may facilitate later removal of the water from the reacted admixture. Whenever an excess of acid is employed over that which is necessary to acidify the clay, it is necessary to remove the excess acid from the mixture of grease ingredients. This is preferably and most simply done by washing the filter residue (pearls) with hot water followed by refiltration of the residue. This acid removal step is, of course, necessary to assure that the final grease product is not corrosive to materials on which it may be used for lubrication.

The following example illustrates the best method of preparing the grease compositions of the invention, as well as the important effect of epoxide-amine ratio and polymer-clay ratio on the high-temperature properties of the grease prepared therefrom.

Example 1 Six polyepoxide coated clay greases were prepared in which piperidine was employed as the curing agent for a glycidyl polyester of Bisphenol A having an epoxy equivalent of 170 and a molecular weight of 340.

Hectorite clay was degangued and dispersed in water to form a 2% suspension. This dispersion was heated to 160 F. and 7% H PO (basis dry clay) was mixed with the suspension. Following addition of the H PO piperend of the high-temperature stability test. Thus the resincoated clay-thickening agent maintained satisfactory grease consistency despite the loss by evaporation of over by weight of the silicone oil. These data also show the beneficial effect on yield obtained, in the case of active hydrogen curing agents, by the use of polyepoxide-curing agent equivalent ratios in excess of about 1.0. By extrapolation, it is also apparent that little additional yield advantage is obtained by using equivalent ratios in excess of about 2.0.

The preparation of polyepoxide-coated clay greases using other amine curing agents and base oils is illustrated by the following example.

Example ll Several polyepoxide coated clay greases were prepared using different amines from both the active hydrogen and catalytic class of amine curing agents. As in Example I, the epoxide was glycidyl polyester of Bisphenol A having an epoxy equivalent of 170 and a molecular weight of 340. The same preparation procedure as Example I was employed. The results were as follows:

Weight Percent wt. Unworked Sample Curing Lubricating Oil Base Stock Ratio Coated Clay Penetration N 0. Agent Polymer in Grease 01 Finished to Clay Grease A Polysiloxane Oil (DC 510). 1.0 10.0 345 A Polysiloxane Oil (DC 510) plus 10% dinonyl 1.0 8. 8 232 phenol. A do 0.8 0. 6 245 A Phenyl methyl polysiloxane Oil (DC 550)... 1.0 8. 1 239 A Phenyl methyl polysiloxane Oil (DC 710)... 1.0 6.9 236 B Polysiloxaue Oil (DC 510). 1.1 9.3 342 B Polysiloxane Oil (DC 510) plus 10% dmonyl 1.0 7. 5 287 phenol. B 0. 8 7. 6 325 B Phenyl Methyl Polysiloxane Oil (DC 710)--. 1. l 7. 8 260 B Mixed isomers of bis(phen0xyphen0xy) beu- 1. l 5. 6 277 zene. C Polysiloxane Oil (DC 510) 1.0 10.0 202 D Polgsiloirane Oil (DO 510) plus 10% diuonyl 1.0 9. 7 258 p eno A=2,4,6-tris(dimethylaminomethyl) phenol.

B =Aminoethyl piperazine. C =Aminoethyl prperazine plus an equivalent part of 4,4-methylene bisphenol isoeyanate. D Diethylenetriarnine.

idine was added to the acidified slurry and thoroughly mixed. Then the glycidyl polyester was mixed into the slurry and the mixture was boiled for ten minutes. The boiled reaction mixture was then filtered and the filtered residue was mixed with a phenylmethylpolysiloxane oil having a viscosity at 77 F. of 475-525 es. and flash point of 575 F. The mixture of oil and polymer-coated clay was heated with stirring to 270 F. to remove essentially all the water therefrom and cooled. The cooled dehydrated mixture was then milled three times. The six resin-coated greases prepared in the above manner were then subjected to a high-temperature stability test.

The high-temperature test comprised heating a thinfilm sample of the grease on a smooth fiat plate in the Example III Using the rocess of Example I, an epoxide resin-coated clay-thickened grease was prepared in which a polymer of the condensation product of polyamines and dibasie acids was used as a curing agent. This material is compresence of air for 300 hours at 450 F., after which the weight loss of each sample was measured and the texture of the grease was observed. The results of these tests were as follows:

TABLE I TABLE III.POLYEPOXIDE-COATED CLAY GREASE Ratio Grease Yield Base 011: Methylphenyl polysiloxane oil (DC-710) S 1 (lpereentwga ltligh-Tergpera- Curing Agent: Versam1d 125 mp 8 c ay to yie ure Sta iit N o. Polyepoxide to Polymer grease having Text, 300l1ou is polyepoxide to curing. agent ,equwalent ratlo Curing Agent to Clay (b 260 unwogked at 450 F. (per- Polymer to clay, welght ratio 1.4

g lgg Welght) Pm) Yield (percent wt. dry clay to give 260 unworked penetration) 5.2 -38 Z-g I claim as my invention: 1 34 1. A grease composition consisting essentially of a 32 major amount of a lubricating base oil gelled to a grease consistency with a colloidally dispersed clay, said clay bearing on the surfaces thereof from at least about 0.7 to about 5 parts by weight, basis dry clay, of a polyepoxide Excluding weight of resin coating. Each of the four samples were soft and plastic at the resin produced by curing a polyepoxide possessing more than one vic-epoxy group with an organic amine curing agent, the ratio of organic amine to polyepoxide being from 0.5 to times the stoichiometric amount required to react completely-the polyepoxide said resin having formed in the presence of a mineral acid in an amount at least sufiicient to acidity the surfaces of the clay.

2. The composition of claim 1 in which the organic amine curing agent is selected from the group consisting of primary amines, secondary amines and compounds containing both primary and secondary amine groups, the ratio of organic amine to polyepoxide being from about 0.8 to about 4 times the stoichiometric amount required to react completely the polyepoxide.

3. The composition of claim 2 in which the ratio of organic amine to polyepoxide is from about 1 to 2 times the stoichiometric amount required to react completely the polyepoxide.

4. The composition of claim 1 in which the organic amine is a tertiary amine, the ratio of organic amine to polyepoxide being from about 0.1 to about 30% by weight of the polyepoxide.

5. The composition of claim 4 in which the ratio of organic amine to polyepoxide is from about 5 to 15% by weight of the polyepoxide.

6. The composition of claim 1 in which the lubricating base oil is a liquid organo-silicone polymer.

7. The composition of claim 1 in which the lubricating base oil is a methyl phenyl polysiloxane oil.

8. The composition of claim 1 in which the lubricating base oil is dimethyl polysiloxane oil.

9. The composition of claim 1 in which the lubricating base oil is a mixture of isomers of bis(phenoxy phenoxy phenoxy) benzene.

10. The composition of claim 1 in which the clay is Hectorite.

11. A process for the preparation of polyepoxide resincoated clay-thickened grease comprising the steps (a) forming a clay hydrosol containing 0.253% by weight clay;

(b) admixing with the hydrosol (1) a strong mineral acid in an amount sufficient to acidify completely the surfaces of the clay, and

(2) a polyepoxide possessing more than one vicepoxy group and organic amine curing agent, the ratio of organic amine to polyepoxide being from 0.5 to 5 times the stoichiometric amount required to react completely the epoxide;

(c) heating the admixture to at least the boiling point of water and maintaining the admixture at such temperature for a period of at least minutes to effect curing of the polyepoxide by reaction with the organic amine;

(d) filtering the reacted admixture to effect removal of at least about 50% of the water therein;

(c) admixing a lubricating base oil with the filtration residue from said filtration step;

(f) heating the admixture of lubricating base oil and filter residue to a temperature of at least 250 F. to effect substantial dehydration thereof; and

(g) milling the dehydrated mixture to form a grease.

12. A process for the preparation of polyepoxide resincoated clay-thickened grease comprising the steps (a) forming a clay hydrosol containing 0.25-3% by weight clay;

(b) admixing with the hydrosol (1) a strong mineral acid in an amount sufficient to acidity completely the surfaces of the clay, and

(2) a polyepoxide possessing more than one vicepoxy group and organic amine curing agent, the ratio of organic amine to polyepoxide being from 0.5 to 5 times the stoichiometric amount required to react completely the epoxide;

(c) admixing with the mixture of hydrosol containing polyepoxide and amine curing agent a lubricating oil in an amount equivalent to at least 50% of the lubricating oil to be contained in the finished grease;

(d) heating the admixture to at least the boiling point of water and maintaining the admixture at such temperature for a period of at least 10 minutes to effect curing of the polyepoxide by reaction with the organic amine;

(e) filtering the reacted admixture to efiect removal of at least about 50% of the water therein;

(f) heating the filtration residue to a temperature of about 250 F. to eifect substantial dehydration thereof and (g) adding balance of lubricating oil and milling the dehydrated mixture to form a grease.

References Cited by the Examiner UNITED STATES PATENTS 2,739,121 3/1956 Weihe et a1. 252-28 X 2,801,228 7/1957 Starck et a1. 2602 2,836,560 5/1958 Teale et a1. 252-28 2,923,696 2/1960 Harwell et a1 2602 2,928,794 3/1960 Belanger et al. 2602 2,928,808 3/1960 Belanger 260--2 3,036,975 5/ 1962 Taub 2602 3,161,114 12/1964 Wittenwyler 2602 FOREIGN PATENTS 563,731 9/1958 Canada.

850,913 10/ 1960 Great Britain.

DANIEL E. WYMAN, Primary Examiner. 

1. A GREASE COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR AMOUNT OF A LUBRICATING BASE OIL GELLED TO A GREASE CONSISTENCY WITH A COLLOIDALLY DISPERSED CLAY, SAID CLAY BEARING ON THE SURFACES THEREOF FROM AT LEAST ABOUT 0.7 TO ABOUT 5 PARTS BY WEIGHT, BASIS DRY CLAY, OF A POLYEPOXIDE RESIN PRODUCED BY CURING A POLYEPOXIDE POSSESSING MORE THAN ONE VIC-EPOXY GROUP WITH AN ORGANIC AMINE CURING AGENT, THE RATIO OF ORGANIC AMINE POLYEPOXIDE BEING FROM 0.5 TO 5 TIMES THE STOICHIOMETRIC AMOUNT REQUIRED TO REACT COMPLETELY THE POLYEPOXIDE SAID RESIN HAVING FORMED IN THE PRESENCE OF A MINERAL ACID IN AN AMOUNT AT LEAST SUFFICIENT TO ACIDIFY THE SURFACES OF THE CLAY. 